I've owned two and they are good little sailboats. Here are some things to look at....
Inspect the keel very carefully before you buy. On most of these V21's they encased a cast iron keel in fiberglass. The fiberglass gets breached and the iron swells and bust it up and then the keel gets stuck in the up position. Redoing the keel is a BIG job. Done it twice.
The v-birth is only useful for storing sailbags or for very small kids.
The boat is light and will move well in a light breeze BUT the wake from a jet ski as it passes in front of your hull (to admire you cute little boat) will cause the V21 to pivot on its keel and knock you 90 degrees off course (ask me how I know this). Only a problem in light air. She really moves well in stiffer wind.
Respectfully, as for the v berth only being good for sail bags or small kids, the same could be said for the v berth on the 25 and 26ft models and most other boats of this size. it really depends on if you can suffer thru staying in a pup tent or if you are looking more for the family sized cabin tent......
we have spent EVERY weekend on my boat for the first three months that we had it and im a big guy. we were comfortable and enjoyed it, but like I posted earlier, it does have a little less headroom.
and although my boat had the full cast iron keel, some of the earlier ones did not. but i have heard the horror stories of some of the fiberglass encased keels.... and it has never been a good experience by any of the story tellers.
and if you purchase it, inspect the keel bolt for wear. you dont want it to break and deposit your keel on the bottom of the lake as some have done... (that falls under the category of basic maintenance)
I never had it round up due to boat wakes, I tuned the rigging to the best of my ability and it always seemed to be a very well balanced boat. (this is saying more about the forgiveness of the boat than it is about my ability to tune the rigging correctly)
and it does move well in light air and can also handle 15 knots fairly well on a lake.... im not sure what it would be like in open water with a longer fetch and bigger waves or swells..... its a nice little boat!