Love the flexibility and customization available. We have found a solid network of add ons that have helped us customize the system without a lot of custom programming on our side.
There isn't much I dislike about the product, it really is top notch. I would like to see stronger reporting capabilities built into the free software. I understand that reporting is a massive beast but the stand alone feature within the software is a bit weak... okay really weak.
Utilize the market for the additional plugins you need. There are a lot of really great developers out there that have plugins that will service most needs. The more you grow the CRM to match your needs the better it will ultimately serve you.
I would also recommend mapping out your plan very carefully. We went through way to many concepts of how to map fields out before we landed on one that worked. Think through each step and then the cause and effect it update will have on your process to make sure you don't end up with a lot of rework.
This software allows us to keep track of all aspects of our workflows, very beneficial. We manage all aspects of our customer lifecycle with the product. We keep track of all contact detail as well as a million other little items we have to track in order to build custom websites. From invoicing and orders right through the final QC we track everything through VTiger.