The Plus had the following upgrades: ultra-low-noise Lace Sensor pickups, a rolling nut, locking tuners, a Hipshot Tremsetter. With the exception of the pickups, all the upgrades are meant to help the guitar stay in tune better.
I love this guitar! I bought it new in 1992 and it's been my main guitar since. I've tried a couple of vintage Strats, a couple of really nice custom shop ones, and a few boutique copies of vintage Strats that I like better. All of these were three to four times the cost of this one when new (used they continue to go for a lot less). In terms of playability and sound quality I have never encountered a non-custom shop Strat manufactured by Fender after 1975 that I liked as much or more. I've also seen many custom shop models selling for as much as $3K which I did not like nearly as much.
I should also say that the older Strat Plus models came with a roller nut that didn't do its job right. Fender sells a replacement nut for these older ones, and this replacement is easy to do and makes a big difference in terms of tone and feel.
People sometimes complain about Lace Sensors being lifeless or cold, but I really don't see it that way. The Lace Sensors have a transparency that lets the sound of the strings, the wood, and your fingers come through even when using lots of effects. If they sound lifeless to you, maybe it's your playing that lacks life.
I admit there's something pretty special about the pickups Fender was putting in Strats in the years around 1970, and someday I might put a set of custom shop pickups in this guitar, but I don't feel any real need right now. The Sensors give great Strat tone, they sound better than most current production Fender pickups, and they have as much personality as my technique. I don't think it's a flaw that they don't have more personality than my technique.
If you want to buy a newer (post-CBS) Strat, I would recommend the Strat Plus or a custom shop model. If you go with the Strat Plus you will have money left over to buy a decent amp.
One last thing, this may matter more to some than to others, but, as you probably know, Fender has usually painted their guitars whatever colors cars were being painted at the same time, and as you probably also know, cars in the early 1990s were often really really ugly. It was the era of the metallic-neon-flash. Fenders from this era can thus be pretty ugly, but I find the sound and playability to be top notch.