Key points to look for in your next job if you are a developer

For Google or Facebook, I imagine you're right in that the ops teams and the internal tools teams are the most exciting, but the products those companies sell aren't exactly super exciting to me, or at least the features they say they are currently working on don't seem very interesting. Perhaps, that's partially because they are both selling a product that is fairly mature. Ad words, search, gmail, and maps have been around or a long time. Perhaps Google drive or google apps still have a few things up their sleeves, but they are also fairly mature products. Similraly, the main facebook features (not ui) have been relatively stable (exceptions that i can think of: likes, timeline, graph).

OTOH, Apple has products at almost the other end of the spectrum (exceptions: the mac pro and ipod classic). On the hardware side, it seems like they are constantly iterating and updating macbook, imac, iphone, and ipad designs. And while I don't like what they've been doing by merging OSX and IOS over the last few iterations, I can hardly say that what they've been doing hasn't at least been innovative. I'd be very surprised if apple had any sort of internal tool that was as interesting to work on as some of the things I just mentioned.

For technology startups like nicera or meraki or arista, I bet most of the interesting work isn't related to internal tools as well, just because I doubt a startup has resources to build very interesting internal tools when they could just deal with what already exists and spend the resources they would have spent rolling their own version on improving the product.

Ultimately, I think the type of product the company sells and how mature their product is (the number of major features left to implement seems like it might be a good rough heuristic) matters quite a bit in determining in whether the internal tools are better than the product in terms of being interesting.

It may be a different thing if you're working on a profit center vs on a cost center I guess. If your clients are outsourcing their software needs to you (so, basically, you are in a cost center), the focus is on reducing the costs of production: you want to deliver as cheaply as possible, no need to innovate. Usually what happens in this situation is that the average joes end up taking the job of building the (boring) product while the best guys build tools to automate the job of the joes, reducing costs in order to increase the profit margin. The innovative work end up in the hand of the tool builders.

However, if you work on a profit center, innovation is the core of the job; the meat is on the external product, and the tool builders just need to automate the boring parts (doing the job the other guys don't want to do.)