I have been a Sony customer for a long time, I currently have a PS1, PS2, PSP and a Vita. Not to mention the Sony stereo stuff too. That said, a few years ago I went to the dark side and got a 360. At the time they had better pricing and a better game lineup over the PS3 IMHO. Honestly I've been happy with it and had no desire for a PS3 (except for God of War 3).
Fast forward to today when I just joined PS+ on my Vita and am currently downloading games. Now that I see the value of PS+ over Live, I'm looking hard at a PS3.
It just seems that Sony is giving me so much more for my money.
I realize this post may come across as fanboyish, but that's not the case. Sony lost me on the PS3 due to price and game lineup at the time I was looking to upgrade from my PS2.
PS+ on my Vita just pushed me over the edge and made me evaluate what am I really getting on my other console.
I say if you can get a PS3 now is a good time. I was like you I had PS1, PS2, PSP but instead of getting PS3 I got Xbox 360 instead. The only reason I got an Xbox 360 at the time was my friend got me Final Fantasy XIII for the X360.
Around a year ago I finally broke down and bought a PS3 Slim because I needed a Blu-Ray player. I got PS Plus for it as well and I love it. PS Plus is definitly better than Xbox Gold, free games and better discounts IMO.
Keeping my Xbox because I don't want to re-buy the games I currently have for it since I still play them. Not renewing my Gold account when it expires unless I can get it heavly discounted since the only thing I used it for was online multi-player access which is free with PSN.
I will say the only drawbacks with the PS3 is that it seems the downloads take longer than with Xbox and I do like Kinect over Move (if you are into motion control.)
However if you plan on downloading a lot (like me) with PS Plus you can set up Automatic Updates and if you have something in your background downloads it will download them while you sleep.
Also if there are some PS1 & PS2 games that you missed out on and can't find the physical copies at a decent price/condition the downloadable PS1 and PS2 titles are a great alternitive. Even though I have a nice sized PS1/PS2 library I have download around 10-15 PS1 titles and about 2 PS2 titles right now. (If only Sony/Bandai would add Digimon World games they would get more money from me.)
If you buy either the Slim or the Super Slim they will not play physical PS2 games but if you choose to download any PS2 Classics from the PS Store those will play on your PS3.
The PS3 is totally outselling the 360 for the past year now. Now that the PS3 is only $199 for a 250GB you owe it to yourself to get one, you will not regret it. I've had the PS3 since launch and never regret getting it over the 360, I knew the PS3 is the superior system in the long run and feel very strongly it IS the superior system.