oh man, an M2 for $700 isn't sticking around for long. I'm not searching for another bike at the moment and I probably still would've jumped on that haha.
I've had a hand full of bikes, mostly Triumphs and Yamahas, but a few years back I had an xb9s, and currently have an S1. I had always wanted an S1, was also a little worried about potential reliability and what not so I opted for the xb instead. It was an awesome bike. I always had wished it was an xb12, and REALLY wished I had just gotten the S1. I ended up selling it. I lived in the city at the time, and despite Buell's claims that the xb9 is the perfect city bike, I'd always come home from rides with headaches thanks to all the time I spent in crawling traffic on a bike that's so closely related to a paint shaker. I also hated it on the highway, but I still rode with guys on sportbikes at the time. I replaced it with an R1, then traded that in for a speed triple(which was practically a perfect bike, but just didn't have the soul that a buell does). I had always regretted selling the xb. This past February I finally picked up an S1. It's pretty much exactly like I had expected. Rough and no where near as refined as the xb, the reach to the bars is a bit further(the xb fit me PERFECTLY, loved how close the bars were) and the seat sucks, but luckily my bike came with a corbin. Aside from that the bike has been amazing. It's died on me a few times thanks to a crappy sidestand switch. Had to have my wife pick me up the first time, I've since realized that putting the side stand up and down once or twice takes care of it, and I'll just remove the switch all together eventually. Other than that, it pretty much always starts on the first try without even pulling out the choke, and for a 19 year old bike that looks like it's had it's share of neglect over the past two decades, it runs great. It's rough, it shakes, sputters every now and then. The brakes stink, it shifts like the internals are made out of cardboard.... but I love it and wouldn't trade it in for anything. I plan on keeping this one for a long time. The bike needs a good going over, which is fine because I enjoy working on the bike as much as I like riding it, but at this point I'm just happy riding it so any random work it needs will wait till the riding season is over. At some point I'll pull the whole thing apart, replace some seals, rebuild the brakes, give the motor a look over, and put it back together so it shines like new. I think I've just hit the age where I can appreciate a bike for being a fun bike, and really have no interest in how much hp a bike makes or what it's top speed is. It's hard to enjoy a 150+hp bike when I'm usually going 30mph in traffic on my way to and from work. The S1 is fun everywhere.
Get that money ready so next time one pops up on craigslist you can just call the guy and tell him you're on the way to pick it up!