Hi Knight,
To tell you the real thing, we have just dumped Tally fully from our company for erpnext and barring a few small things, which would be implemented in the near future, this erpnext system is way better than Tally or BUSY.
To point out a few of the amazing things of erpnext which we love:
1. You can assign any thing to a user and set is a TODO thing (not possible in both)
2. Manage your accounts from any where in the world if you setup in a internet based environment (not possible in both)
3. Add unlimited number of custom fields easily (though you need to learn some part, but in Tally you need special TDL for which you need to call a developer even for a small addition)
4. Add conditions to fields like make them mandatory (others don't support it or support it through specialized customisations)
5. No software needed for installation (you just need a browser Chrome or Mozilla freely available)
6. Can be used on linux or Mac or windows or even note books, I am actually using this on ipad as well (not possible in both)
7. Work on multiple windows which in not possible in tally or busy
8. Make your own reports (you might need to learn a bit of mysql or javascript for that but they are easy to make)
9. And there are many other things which I can go on and on
To cut the story short, I am one of their customer only and not making a sales pitch but honestly have never seen such a product. But I should also tell you some negatives of erpnext which are there since no product in the world is perfect:
1. Since the product is open source and the updates are pushed regularly almost everyday hence there are times when you would encounter bugs, which I should admit have become much less than what they used to be during updates.
2. The accounting module is still not as strong as Tally but even then I see that this product is way better than tally or busy.
I can't really think of other negatives since the quality to price ratio of this product is one of the highest in the world and I am in no way exaggerating this fact.
So I personally think that if the company has the will to transfer they should transfer to erpnext and they would not regret their decision.
Now I have used both the softwares