we are running our own BES on Domino with some real BBs, but I tried BB connect, GL, and MS Push (with EXCH) on the E61 and other devices (Treo, 9300).
In my opinion, BB connect is useless, unless its not BES 4 compatible. MS push, albeit I don't like it, behaves better. I HAVE my contacts synchronized two ways. But to be honest, the best way to go if you don't want to use a real BB is GL. GL is giving you what you may expect from BB connect.
But today, I ordered a 8700g. I don't want to miss a true BB