For me, you already answered your own question.
"It feels nice, plays well."
Then it's worth it.
This x 100!
You do need to exercise some common sense however. My rule is usually to confine fixes to easy things like replacing a pickup or doing some rewiring. Once you start getting into replacing mechanical things like tuners and bridges, or replacing a neck, it can get expensive fast. So you have to put a stake in the ground. Otherwise you start piddling away money that could have been better used getting something else. Because it's like a car. There reaches a point where you can get better - for fewer hassles and far less work -
and for less money - by just replacing it.
I approach refurbishing things the same way I approach mods.
Let me give you a recent real world example that happened this week:
I bought a Squier Matt Freeman PBass not too long ago. I liked it just the way it came. It played well and sounded really good. But I got bored a few nights ago as I was rummaging through the store of parts I've been collecting since forever. To make a long story short, I decided to mod it. So I wired up a completely new electronic assembly consisting of an an Aguilar AG-4P-60 pickup, a couple of Emerson Custom Pro pots, a Switchcaft jack, an orange drop cap, and a new pickguard plus two new chrome knobs.
I keep track of the value of every item in my parts collection. So I know that mod cost me about $150 all in. And there wasn't going to be any option to recoup money and offset the expense by selling the original parts. Because I may decide to restore it back to stock some day.
So $379 for the bass plus $150 for the mod equals $529 current investment in that particular bass.
Would I have bought that bass to begin with if I went in with the intent to mod it because I didn't like it the way it sounded or played stock? Nope. I would have looked for something
else to buy. Because that extra investment required would have put me in striking distance of getting something fancier (although not necessarily better) than that Squier. There's quite a few nice used MIMs and MIJs to be found in the $600 range if you shop.
If I hadn't gotten bored, would I have modded it anyway? Nope. I liked it the way it was. Why spend money or time ditzing around with it if that were the case?
I definitely wouldn't have done so if I actually had to go out and
buy anything. But I had some time, and all the needed parts (and I could always flip it back) - so what the heck? (For the record, it sounds and looks really really sweet in its present incarnation. So I'm definitely gonna leave it that way for the time being.)
So how does this apply to a decision to refurbish a beater? Easy.
I ask myself two questions:
1. Can I get something better out of
something I already like without having to go out and spend too much (or any) extra money?
If the answer is yes, I'll consider refurbishing or modding it.
2. If I'm bored - or I just want to do it - should I do it anyway?
The answer is also yes - as long as I'm not being silly and spending large amounts of money on something not worth fixing; or wasting excessive amounts of time on it when I could be playing or practicing.
There's always going to be exceptions to the above. But as a general rule of thumb, that's how I roll. YMMV.
Oh yeah...since this is TalkBass and it's "pictures or it didn't happen" - here's the lady in her new outfit:
Note: that pickguard is dark red flake -
not tort. Sorry for the lousy picture.