Very nice. I'm sure he'll grow quite well. As has been said, they're tough little animals.
The first of my two rescues was one I assumed would not survive. She had been kept in a ten gallon tank on fluffy hamster bedding with no heat source in a cold room with an algae-filled water bowl and one half log hide. Took me over one year to convince the owner that she'd benefit from me taking her, but I couldn't give up. At two years old she (keep in mind female) weighed in at 250g.
She has never refused a meal and is now pushing 800g. Poor thing couldn't eat because she had no heat to help her digest the food offered. Plus, here's the kicker... they microwaved the small frozen mice they offered her.
Rescues are quite fun, in my opinion. I love seeing them months later and comparing the first pictures taken of them.