GMail is really cool. I mean REALLY cool. There are products you hate, and never use; there are products you hate, and use because you have to; there are products you use regardless of their shortcomings, because they have features you want; and then there are products that are so close to perfection they are no longer a product, but an extension of your work/play.
GMail falls into the last category. It has an intuitive user interface, and makes great use of emerging web technologies, like XMLHttpRequest (aka "Ajax"). I like GMail better than Outlook, Outlook Express, Thunderbird, Mail.app, or pretty much any mail program I've used to date, and I've used a lot of them. And what's more, it's free, it stores more mail than I would ever need to store, and I can access my contacts and messages from any browser, anywhere.
Google Groups falls into the third category - it has it's pros and cons, certainly, and while I'm not a big Usenet guy (I used to be, until AOL added Usenet access and it all went to h3ll), I find it to be the most effective option, for me. Plus, again, having roaming access to your subscribed groups is an advantage.
Google search falls into the third category, through no fault of Google's. Quite simply, this is the fault of a) trying to search the unimaginably massive contents of the internet, and b) unscrupulous website maintainers doing their best to sneak their way up Google's search rankings and ruin your search experience. I think Google search is by far the best out there, and I think significant technological improvements to the web in general, such as semantic tagging, are the only way that Search is going to improve - and maybe not even then.
Add to all this Google's ever-growing list of features - maps, image search, phone listings, math & unit conversions, weather, you name it, Google's got it, or it's in the works. Google is the all-singing, all-dancing God of the Internet. The only things I can think of that Google needs are more GMail-like personal features - a calendar, bookmarks, to-do list, notepad. Partly because I've seen how good Google is getting with web applications like GMail, partly because the solutions that exist currently aren't as good as they could be, and partly because these are the kinds of things you want to be able to access from anywhere, not just from home.
What I would really like to see is a fork of Firefox, a sort of Googlefox (G-Fox? Sounds like a rap name...), that gives me Google's everything-search close at hand (not just a little web-only search up in the corner), that uses GMail as my web client and Google Groups as my news client, and, assuming they put together my wish-list of features above, integrated those as well. At first I was thinking of a Google Portal - I know, I know, let me explain. Not a silly hodge-podge portal like Yahoo! or any of the millions of its clones, but a true personal portal; not a page full of ads, horoscopes, and jokes-of-the-day, but a real *me* page. Give me a Google search box, an RSS feed of my GMail inbox and my Google Groups, a compose button for each, my selected Google News sections, my Google Alerts, my local weather, my blog, my photos, and so on. If they'll keep track of my bookmarks, let me do a personalized search using my bookmarks as a reference to personalize results.
But then I thought, no, Google would never build a portal. It's against everything they stand for. Google is all clean interfaces and uncluttered pages, not something a portal page is suited for, even an extremely well-done one. Then it hit me - okay, Google doesn't have to do it. They can just offer the services, and let the OSS community build a FireFox browser that uses the Google features. Keep the great services and data mobility, and give you access to all of it at your fingertips using the Google browser, or, if you're on a public/work machine, you can still get at all of it the old-fashioned way. Plus, this lets you keep Google with you everywhere you go on the web, telling you about new mail, offering you related links, and so on.
It's funny - I would happily have Google follow me everywhere I go on the web; yet that's exactly what I, like many others, have strived to avoid with Microsoft. I beg one company to do it as I beg another company to stop. Go figure...