Well, it's hard to predict about the future, but I can tell you a little about my experiences in the past. Generally the DH service quality has been very good, though there have been a few occasions of big problems like DDOS attacks that took some hours to some days to clear up, or a power outage even. These are things I hadn't experienced with my earlier hosting providers (them being small unknown companies with few an unknown websites). I think these things happe n to DH mainly because they are so big and they host so many sites. More sites = more targets for attacks. They do a terrific job of informing customers of the current status, even if it's as frank as "we screwed up", and they are usually fast to clear up the issues. Mind you, my sites are not commercial-grade and so I don't worry about these occasional incidents. General Motors would probably not host with DH; they'd do it themselves.
The frequent slowness of the DH Web Panel and the occasional unreachability of it is the only thing that really tends to bug me. The Panel itself is good, feature-wise. I haven't tried the much-touted "cpanel" but I hear the DH Panel is better, though it could use a code and design rework.
Mail service has been up practically all of the time, except during the DDOS or power outages. The junk mail filtering is very valuable, too. It's not bullet-proof, but without this initial filter, I'd drown so badly that I could stop using mail altogether.
So, will it improve? I don't know, but I feel that the current state is a group of problems that are working together against us and DH. I expect that they will have this fixed at the end of September, and then it will be back to normal -- that being "not 100% uptime, but recommendable for non-critical hosting".
[color=#CC0000]Get $50 off[/color] with promo code "LESS"! See here what else you get!