The Lyman GPR is probably the best buy available today.
It is a good rifle as it comes but it can be made into a really good or great rifle easily.
I did not experience the poor shooting barrel(s) so many complain about here. My flint and/or the cap lock shot well right from the box.
Now for the issues:
On the flintlock model the lock is not very good. It works but not what I consider good. The touch hole needs drilling to 5/64th inch.
The cap lock is OK as is. The nipple is trash. Get an after market one.
It is better looking, if not improved shootability, with the installation of the provided primitive rear sight. And a additional cost silver blade front sight.
Now for the trigger, just get a Davis Deerslayer and be done with it.
Fit and finish is poor to OK. You may want to get the kit version and you can improve both if you are a little knowledgable in wood working.
The barrel is the best thing about one. Oh, BTW, get 54 cal.
Like I said you can make a good start into a really nice rifle.