Limited from what I saw. Its miles better in Soldeu, especially at the moment as it dumped over 6 feet of snow in the last week. You can't get in Via France at the moment tho (
Depends how 'experienced' you are, there is a great area called 'the avalanche 'with some great off piste rides, some instructors take advanced classes there at the tail end of the week, with the odd hike, and the right guide!!!! (dont do it on your own) there is loads of scope for off piste
ps make sure your insurance covers off piste just in case!!!
Under the new 4 man chair there are some runs through powder and trees, Avalanche is pretty cool, more of a straight blast than anything special but it had some fine powder there last week.
All in all Borovets is pretty limited unless you want to hike, not fun with no snow shoes... I tried pant pant pant!!!
The avalanche is ok at speed, under the 4 man chair to the right of the resort is ok if quite tight, (best after a heavy new snowfall).
Pay a little extra and hire a guide for a morning, he will assess your competence and show you areas suited for you. Dont expect the 3 Valleys etc, but its a hell of a lot cheaper so just enjoy what there is!