VISION
Impulse Visions are great! I've had one for a fair time now and head no problems at all, I also had a standard Impulse before that (same mechanics) and had v. few problems with that. The best thing about the vision is that yopu just CAN'T break paint. The support from SP Europe is second to none... the warranty covers anything that can go wrong for the first year I think and Nick, Phil or Ross at SP Europe will happily sort out any problems if they do arise. There are no common problems that I know of... all u need to do is read the manual and it explains clearly how to use the vision eye etc... The main thing to remember is not to have your input pressure above 200 psi. Maintenence is minimal.... I give mine a quick clean after every day's play and some new grease and that's all it needs to be kept in perfect working order. The one upgrade that I consider really important on a stock impulse is a new trigger / trigger job. The Eclipse Blade is great and u can get them from Planet for about £15.
Website wise, there's a really good Impulse FAQ....
http://www.kamworld.net/paintball/ImpulseFAQ.html
The FAQ should answer most of your questions and discusses upgrades etc.
Hope this helps
Kieran