I've played golf in 42 states as a single. I travel for work and for pleasure and usually take my clubs. More often than not I've been paired up with others but have also had hundreds of rounds by myself. As a rule, people I've been paired up with have been fun to play with and I've met a lot of interesting people. Golfers tend to be nice on the golf course even if they are A-holes off of the course. There's a book titled "Blue Fairways" that tells the tale of the author's (Charles Slack) solo golf road trip from Maine to Florida. It's a fun read that you can pick up for a buck or two used on line.
The biggest negative about playing as a single is if you don't get paired up with others and get stuck behind a bunch of foursomes. In that situation even a four hour round will feel slow. If I'm about to be sent out as a single and there's a group less than four on the first tee or on the first fairway, I always ask to be paired up with them. I've only been turned down twice. Once was by three novices who were embarrassed to play with strangers,who let me go ahead of them (Thank God) and once by three "plus" handicaps who thought I'd slow them down. After several holes of me waiting to hit my approach shot while they checked their putts from ten different places, they finally let me play through. By then there was a two hole gap before I ran into another group who asked me to join them . When I get stuck behind several foursomes I often play two balls on each hole as a match - one ball against the other. If its just one or two groups ahead they's usually let a single play through. If you don't get invited to play through and you think there's a gap in front of them ask them if you can skip the hole and jump ahead of them. When you do that they'll either let you play through, jump ahead, or let you know there are other groups ahead and nowhere to go.
The best ways I've found to avoid getting stuck behind a full section of the course are (i) book the first tee time of the day, (ii) book the first twilight tee time (people tend not to book just before the rates go down so there will likely be open holes ahead except on the busiest of courses) and (iii) if the earliest few twilight times are booked, take the first open tee time preceding the time that twilight rates start.
The second negative I've encountered in booking as a single is that some of the courses I want to play don't allow singles to reserve a tee time in advance. That's becoming less of an issue since most of the on line booking systems are now sophisticated enough to open up partially filled tee times so singles are able to join existing twosomes and threesomes. However, those times don't always meet my schedule and sometimes I want or need to finish out my itinerary and I sometimes can't wait until the day of play to get on to the tee sheet. Begging has worked on occasion in this situation. I wanted to play the Berkshire outside of London for many years. They have a strict "no singles" policy. After several trips to England with no success convincing the club secretary to take my name and fit me in anywhere, she finally felt sorry for me and let me go out before the first tee time of the day on the Blue course and before a "society" (group) event of the Red Course that afternoon. It was one of the most delightful 36 hole days of golf I've ever played. Of course there are a few courses like Muirfield that you'll never get to book as a single.
Booking as a single has some positives too. It gives you the flexibility to play when and where you want. You can book at the last minute if that suits you and you don't have strong preferences for a particular course at a particular time. You can take advantage of the best "last minute" discounted tee times on Golf now and the other booking sites. It also makes it easy to get replay rounds since the course can fit in a single much easier than a foursome.
The last round I played in 2017 on a family trip to Orlando was as a single while my wife and daughter stayed at Universal. I got paired up with former PGA Tour player Wally Armstrong who is now a great teacher known for using lots of teaching gadgets. He was giving a playing lesson to an investment banker. It was a hoot. It turns out that the banker, who lives in Florida has two sons who work in my building in NYC. I've had dozens of "small world" encounters like that while playing as a single.
Last summer I did a golf trip as a single through Kansas, Oklahoma, Arkansas and Missouri. In OK I got paired with a former US Champion shooter (clays), In LA I once played with Marcus Allen and Frank Robinson was in the group ahead of me. On a vacation at Bay Hill I got paired up with a husband and wife. They were nice but not very talkative and we were only introduced by first name. By the third hole we figured out that I knew the husband for a dozen years through work but we had only spoken on the phone. Last year in Scottsdale I got paired with a doctor whose colleague had performed surgery on my son one month earlier. I've stayed in touch with a guy I met on a course in Wisconsin 15 years ago and I've seen his daughters grow up through social media. We stay in touch and vow to play again. Lots of good memories from rounds that I booked as a single
edited to fix typos
Edited by sabram, 6 minutes ago.