The Nokia 5110 is the first mobile which I have handled and I am all out for it...albeit its heavy and a bit bulky compared to the other models. It is more than sufficient in all its features, and would definitely recommend it to others. Only suggestion would be to use a thinner lithium battery pack which makes is much lighter.
The only drawback is that the battery tends to get a bit loose and this can cause a problem, sometime. This might be remedied by using the thinner and lighter battery which makes it much more compact.
Would recommend it to users, definitely.