Everything you've stated is correct and is expected, the situation is much better for 1.9

In 1.8 I have solved these issues for high volume sites by deferring the sending of emails to the system shutdown handler with the vroom plugin.

OK.. Thanks.. Waiting with 1.9 release with expectation :)

Further analysis showed some of my stupidity. My delays were increased because of the configuration of the MTA. It was processing way too much in foreground and not returning control to elgg. Once I changed the config to increase background processing, the delays were greatly reduced. 

There is still an idelay ssue with users clicking buttons more than once because of the delay from "Save" to a screen refresh, but I have enough of a solution until 1.9 I believe.

Brad

Quick :) question (no such thing)..

I looked at Vroom and it looks like it could be interesting short term. Not sure I have the skills to do it.

I want to implement it for group discussion notifications. Discussions are a little special from what I can determine.. 

Seems like I need to change start.php in mod/groups

if ($interested_users && is_array($interested_users)) {
                                foreach ($interested_users as $user) {
                                        if ($user instanceof ElggUser && !$user->isBanned()) {
                                                if (($user->guid != $poster->guid) && has_access_to_entity($topic, $user) && $topic->access_id != ACCESS_PRIVATE) {
                                                        $body = elgg_trigger_plugin_hook('notify:annotation:message', $annotation->getSubtype(), array(
                                                                'annotation' => $annotation,
                                                                'to_entity' => $user,
                                                                'method' => $method), $string);
                                                        if (empty($body) && $body !== false) {
                                                                $body = $string;
                                                        }
                                                        if ($body !== false) {
                                                                notify_user($user->guid, $topic->getContainerGUID(), $subject, $body, null, array($method));
                                                        }

The notify_user line needs to change to something like;

if ($body !== false) {
elgg_register_event_handler('shutdown', 'system', 
    function () use ($user->guid, $topic->getContainerGUID(), $subject, $body, null, array($method)) {
           notify_user($user->guid, $topic->getContainerGUID(), $subject, $body, null, array($method));
    }
, 500);
}

All normal disclaimers about not changing core elgg and this is a completely non-prod instances which I can easily break and restore.